The overall objectives of this project are to investigate cellular and genetic mechanisms in the induction and regulation of murine cell-mediated immune responses to alloantigens in vitro. The work is focused primarily on the function of alloantigen-activated murine suppressor T cells in the control of mixed leukocyte reactions and the generation of cytotoxic T lymphocytes. In addition, we will identify and characterize genetic loci that can induce such response, both within, and adjacent to, but outside, the H-2 complex. Cell surface features of T lymphocytes producing and responding to molecules elaborated in the regulation of in vitro cell-mediated immune responses, as well as the physiology of such cells will be investigated in detailed. Regulatory interaction between cellular subpopulations both in the induction and regulation of these responses will also be explored.